&DRIFT: PLOT-FIELD
All functions in the description of the PLOT command (f1, f2 ... f6)
may depend on the following set of variables:
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Symbol Meaning Note
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X, Y, Z Position R, PHI for polar cells
EX, EY, EZ, E E-field at (x,y,z) ER, EPHI for polar cells
BX, BY, BZ, B B-field at (x,y,z) only if there is a B-field
VDX, VDY, VDZ, VD Local drift velocity VDR, VDPHI for polar cells
LORENTZ Local Lorentz angle
TIME Total drift time
PATH Total drift path length
DIFFUSION Integrated diffusion only if data is available
AVALANCHE Avalanche multipliciation only if data is available
LOSS Loss due to attachment only if data is available
STATUS Drift line status code a number, not a string
P Pressure of the gas
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Other variables can be added on request.
Produces a plot of the lines of equal function values. The contours
are labeled with the function value if the LABEL option is on (which
is by default the case).
The function is computed on the part of the viewing plane that is
located within the current AREA box.
If you request AUTOMATIC scaling of the range, contours are drawn
at decent function heights covering the range of the function on the
AREA. The number of contours is used to compute a rough distance
between two contours; the distance is rounded downwards. The number
of contours actually drawn may therefore be larger than the number
you request.
Note that much better equal time contours can be obtained with the
DRIFT WIRE ISOCHRONES=delta NODRIFT-PLOT instruction which takes the
end-point of the drift lines into account when deciding which points
of the contours are to be joined with a line.
[The default function is V, the drift velocity, and the contour range
is by default adjusted automatically. By default, about 20 contours
are plotted.]
The function is evaluated on the track or on the curve specified
with the ON keyword.
The geometric aspects of the track, if used, should be set by means
of the TRACK command before calling PLOT. Other aspects of the track,
such as the clustering model, are not used in the present context.
A curve should be parametrised in terms of T which will run from 0
to 1. All 3 coordinates of the curve should be specified. Note that
ON expects only one argument, the parametrisation should therefore
be enclosed in quotes, e.g. 'cos(pi*t),sin(pi*t),0' would be
appropriate to describe a semi-circle in the z=0 plane.
The SCALE option can be used to force a vertical scale in the
plot, this can for instance be useful if you intend to overlay
various graphs.
If you select the PRINT option, then the values plotted in the
graph will also be printed out. Output re-routing (> file) can
be used to write the values to a file.
The number of sampling points can be set with N, default is 200.
[The default function is V, which in this context stands for the
drift velocity and not for the potential !]
The function is sampled at GRID by GRID points on the part of
the current viewing plane that is located inside the AREA box.
The function values are entered in an histogram.
This kind of plot can be useful to estimate for instance the
spread in drift time over a given region.
The automatic search for proper binning (AUTOMATIC) uses the
first few entries to set the range. Since the grid is scanned
in a regular sequence, these entries are not necessarily
representative for the entire sample, in particular if the
number of bins is small compared to the grid size. See CALL ->
BOOK_HISTOGRAM -> options -> AUTOMATIC for details on the
automatic binning procedure.
[The default function is V. The number of bins is preset to 100 and
the range is by default chosen automatically.]
The function is sampled at GRID by GRID points on the part of
the current viewing plane that is located inside the AREA box.
The function values are presented as a three dimensional plot.
The plot is first rotated by phi degrees around the z-axis and
then tilted by theta degrees from the z-axis.
This plot is decorative but it is generally agreed upon that it is
hard to extract any meaningful information from it ...
[The default function is V, i.e. the magnitude of the drift
velocity. The default viewing angles are 30 and 60 degrees.]
This plot shows the flow of a 3-vector sampled at GRID by GRID
points on the part of the current viewing plane that is located
inside the AREA box. The vectors are displayed like geometrical
objects.
The z-component is set to 0, if not explicitely specified. For
other than (x,y) views, this may give incorrect impressions.
It is advisable to have roughly equal ranges in view of the scaling
that is performed on the vectors.
[The default functions are VDX, VDY, VDZ, i.e. the drift velocity.]
Requests drifting of electrons, not ions.
[This is default.]
Requests drifting of ions, not electrons.
[This is not default.]
By default, electrons are drifted with negative charge and ions with
positive charge. If you wish to see the origin of the electrons and
ions arriving at a given position, you may wish to reverse the sign.
The POSITIVE option forces the charge to be positive, no matter
whether the particle is an electron or an ion.
By default, electrons are drifted with negative charge and ions with
positive charge. If you wish to see the origin of the electrons and
ions arriving at a given position, you may wish to reverse the sign.
The NEGATIVE option forces the charge to be negative, no matter
whether the particle is an electron or an ion.
Keyword index.
Formatted on 10/11/98.